A large number of t h e abetracts have not been checked with the original papere but have been included becauge they offer 8ane inforc mation which m i g h t be of interbat. Beferences that have not been checked a r e marked with an asterisk, and the 8ou~c8 of the abstract l e Included Jut beluw the abetraot. Sane editing of the unchecked abstmots wa8 perfamed w h e n cLarity.could be improved w i t h o u t loss of accuracy.

METBOD OF PRESENTATION

Abstractfl

The main headings have been designated tis GBNERAL IN3URMATIONJ fMIROSTATfCS, HyDRODpNAMICSJ AERODYNAMICS, OPERATION, and RBEKRCH. The GENERAL INFORMATIOPT claeeiflcation is concerned with bibliographical references and referenoes i n which the mrfommince or geaPnetrical c h m c t e r i s t i c s of seaplanes a r e described or dlscusaed in a very general. my. Referenoes that deal with a seaplane a t . rest I n the water are ClaSeifi8d under HYDElWI!ATICS. EYDRODYNMCS, which is the:main subdect under consLderstlon, contains referencee that relate t o the characteristics of a seaplane frcm rest t o getaway. AERODYNAMICS inoludee inf'ormatica on t h e aerodynamic chara c t e r i s t i c s that direotly or indireotly influence the deeign of t h e hydroayneLmic ewfaces, O ~ T om It a i n ~ e those rei'mences In which t h e conditions unaer which seaplanes must operade are described. Reference6 t h a t relate t o the manner i n whioh reeearoh ie carried h e equiplent ueed are c l a e e l f l s d under RESEARCH. out and to t

Side force 'Heeling mament

Abstraotors notes are enclosed by braoketa.

& hydmdynadce, a8 in other f i e l d e of research, the mnes of the authors are very uaeful in l o c a t l n g inf,tian of e type for which an authar i s w e l l known. The names of %he authors of the papers @veri a r e therefore indexed alphabetically. After the name of eaoh author, a list of abstract numbers, is given indicating the repof w h i c h he was a W a r ar coaubhor.

index3 f i not intended to .be acaqplete hut inoludes the factore that; ^. appear to be of most Interest to.seaplane specialist^. . .LISSY.

for long distance overwater alr~service.' It i s believed that i n sizes from 50 t o 1 0 0t a m the flying boat would have equal cruising epeed combined with greater pay load OF longer range than a landplane of sfmilar size and power. Design factors are offered t o show 'that,the pay load or range d i f f e r e n t i a l should be approximately 20 percent."

Cowidere~tian i s given mfiinly to hull and float shapes and chgraot,eristlcs, and the results of n w r o u s tank t e s t s are given graphically showing resistance and n t as fuactione of epeed and trim. The observed dietribution of pressure 011 a flat p l a n a surface at 10* trim IS plotted 4 3 6 a f a l y of c m e s of congtant, pressure. %+float seaplanes and flying boats are conpared and t h e manner i n which t i p f l o a t s increase in s i z e as the airplane i 8 made larger i4 describe&. The effect of nonetandard atmospheric ConditiOnS on the takc-oif of B b t OT Seapun9 is diSCUSE8d with the aid of oharts. A number of aircraft deai-8 are dfSCU6Bed anti photographs are included.

fuing

..34

NACA

RM No, L7J3.k

Details of t h e deeign, engineering, construction, and performance of the Blackburn '8.20 are given, The D.20, wMch was ccanpleted and flown in l g b , incorporates the patented feature of a planing bottom that is retractable. TRie planing-bottom portion of the hull ia.separated fram the main eection, on wwch it is mounted, by m e a m of a set o fn l l k e . The Iiake are 80 proporticpled t h a t in the extended position of the planing bottcon, the hull and ving aeaume the beet attitude for take-off, while in the retracted posi.t;ion t h e planing bottcaa or pontoon fits snugly to the hull in a t r e w i n e oontoure,

Calculations were made of the the t o tak.e-off over a range of grose weights. The suitability of throttled take-off teste for predictiw t h e U m i t i n g weight a t which a mrmplane can take offWas iatre0tigit%dm

I.

The loee of hull efficiency due t o fittiw either inboard floats or etubxlng etabilizerer In place o f ' wiq-pt3.p floats I s very g r e a t , and in this investigation amounted t o a reduction i n pay load of 9 percent and 17 percent, respectively, for a tak-ff' o f ' 6Q seconds i n oalm o ~ n d i t i o ~Errore , of the order of 2 percent . m y result if throttled tako-affs a t nonnal Iced are used for predlctlng the llaaximwn weight a. t which a eeaplane .can be taken 'off * in a reaeonable time,'

'

.. Take-of'f times were obaemed of three eeaplsnes in winds varyiw frcen 0 to 3 0 percent of the take-off epsed, and of one seaplane in winds varyin@r from 0 to 40 percent of the tak-ff speed and i n tailwinde. The reeulte of the tests showed khqt the take-off' time and dietance of a-seaplane In zero w i n d are giyen by the equationsL

the t a k d f f tim of t h e Short Singapore I1

for a gross weight -of 26,goo pounde no wind, and t% effect of wind on the maxinm grogs Wight. at whioh the P l y i n g boat could take off. The caarrputatfonis wePe Meed- ga -tank teste of 8 model of the' h d l and wind-tunnel %est's of a m&l of %he 'flying boat. . .

fly&% boat were made t o detemdne t h e effect

of

w a g incidence

" -

- .*

-.x:

The caloulated take-off tirces agreed well with the times observed for sevmlnorma1 take-off's of the f u l h i z e flying boat. . The addition of a .virtual mass of 22 p e r c a t , of t h e load on the water In the calculations gave very good agreement between the calculated and observed take-off times, The results of the computations showed that the take-bff tines would be reduced by 1 1 - second6 by maintaining best trim, and. tkt the time would be 2 further reduced.by 2 s e c d s by maintaining beet trim and by . increasing t h e wing incidence. Increaelng the wfnd speed from 0 t o 20 miles per hour increased the maximum weight at which the flying boat could take off frcpa 32,600 to 34,600 pounds.

*p. Crocco, G . A. : Tim

Criterions for calculating the take-off and landing t i h e and distance of airplanes and seaplanes are brought up to date by recent data on the variable pitch propeller, flaps, aerodynamic braking, and models of floats.

deutechen Luftfahrtforechung, Lfg. 9.

The time and..distanoe required for the take-off .of seaplanes are ihportant ,quantities in the ,perfomme of each type. .After 8ehort .dis,cuElsion of the prooedurger and the usual method used A n . t a k h f ' f calculations, a.q m l e approximating method l e given, by I which the meaeuremeslts taken pwlng ta$e-oPq under varloqs weather COnditi~m6can be reduced to other omditlam of aperatlop, euch a8 no wind and sea-level conditions. Author . . . . c .. .'I .

HYDROSTATICS Buoyancy

. . The gross weight and thelongitudinal po8ition.of thecenter of gravity of the model were varied by means of a weight placed on the'deck, Flooding of cnmpartments wae simulated by adding weights on the deck. The weight o f - t h e additional weights was q u a l t o the lose of buoyancy of the flooded capartments and the resultant center of gravity of the weights was d i r e c t l y above the center of bubyancy of the flooded portions of the floodedcmpartments. The r o l l i moment ~ wa8 applied by means of off-center weights or by forcet3 directed upwards. The vertical position of t h e center of gr&vity:wae not t o scale, but i t a effect wa8 corrected for i n the rolling t e s t s . .

I A the propoeed design, a universal Joint give6 the tip freedan of movement in a vertical and horizontal plane. The f f n keep0 the float autcapatfcally head on to the flow o f . t h e and in the air, h&d to the wind. S m a l stub'winge give t h e

floattail

water, float

the necessary longitudinal. s t a b i l i t y in t h e water, otbmiae, as the float is free on the universal Joint, it would. be inclined to hunt in'tbe water. Retraction of the float lnto,thewiw 9srecammended ,

The hydrostatdo s t a b i l i t y is determined for a Vought V-85-C seaplane. The t e s t s included lateral .and longitudinal,. inclination on a model for 2100. &d 2 3 0 kil,(4630and 5070 pounds) 'groes weight. The effect 'a? the vertical location of'the w i n g floats on lateral stability is also examined. I t is found that any r a f s i x of the wing f l o a t 8 has a bad effect on the stability .about . the longitudinal exie. . . .. Author"

Notes are given which m a y be of uae to aeronautical engineers when planning disposition of floats In seaplanes or flying boats; accurate estimate can be-made by methods given, in order to find righting oouple that will be available to counteract any upsetting

In a.vertlcal plane creates

The added m ~ s aof rectaqplar and triangular.prisms floating In . water l e found in conneotlon with an investigation of the natural. frequency of l a t e r a l vibration o f a 8hip's hull. The ewerimental values are compared with those yielded br calculation.

Sci. Abstr, 1930, abstr. 3006

317. Brahmig, Rolf:

. The methods for determining virtual mass under conditions o f linear and vibratory motion known up to t h e preemt are brfefly described. For the study and numerical representation of purely hydrodynamic Inertia effeuts on oscillating bodies, a simple test method for forced vibrations is r8pWtbd and' illustrated by tests on vibrating disks. In oonverting the reeulta of model teqts t o full scale, principles o f eimllitude m u s t be considered. Thee are given for the simplifled case of 8 ship propeller YibratLng harmonically parallel to t h e f r e e surface of an undisturbed fluid.

[The possibility of cavitation I s not mentioned.]

7 3 . 8 . B a r n i l l a , E. G . :Div

. 3 . of Springer (Berlin)

~ d r o d p E U n i C 8of

Aerodpunlc Theory, W.

1936.

B o a t 8 and Bloate. Vol. F . D u r a m l , ed. I Juliua

K C J

A r6sw' of the hydrodynamlo phases of' martne aircraft penformance is given.

Chagter I givea a general view of t h e conditions imposed on seaplane6 at rest and during take-off and Mute i e r made of the eignificance of t h e step and the part it plays in facilitating

land-.

take-off.Chapter I1 describes take-offsand water oondltlons:

and landinge under various wind Graphical representation of takb-of'f by llbeane

573YDRODYNAMICS

Generalof curves of thrust, resistance, and t r m mment plotted against speed is shown, and the detemination'of take-off t i m e and Ustance from these curve8 is deecribed. ..

Chapter I11 contains a m e detailed account o f ' take-of'f and resistance. The wave formation produced br.a seaplane c z planing surface in mtion alorg he surface of the.water.is Bisou6sed. A discussion is given of t h e take &f of a ladderlike .series, ofa vanes at constant trw, a d of a ocanbination of wing and 'planing Burface. Results of experiments on p l a n a awfacea by Frow5e' and Sottorf, and on p r i m t i c floats are'discueeed. The effects.on resietance of beam with constant length and of center-of-gravity poeition are mentioned. .. .

. .

The difference8 'betyeen landplanes a* eeapla&e with refeonce. to-the aerial portldns are dfsdusserl In,ohapter I V , and differences and analogies between'formi for'seaplams and planing water craft are discuased In cha2ter y. Chapter ,a oontatne a . deecl'lption of~calculationsof Buoya~cyand statio stability. .The .a directLoaa1 stability of a seaplane' when &rifting, moving forward under pow8r, and being towed are discussed briefly i n chapter ~esult6~of~Iiumpler*s method of' debmining the principal characteristics - w i n g area, gtructural w e i g h t , and paylaad of a seriee o f flyiw boat8 of varying gross weight 831'8 conpared with a series built 'by Dornier In chapter VIU* Procedurea and equipment used in tests of reduced-ecale models, and water presmre.distribution on a hull are dieouseed in chapters IX and X, respectiYely. The desirability 09 more cq1eta.theoretfosL f3O'lutiOlI6 o f the two-dimeneioaal and three-diraeaeibnal &aning proceeses and Sottorfte analysis of the frictional, induced, arid wave-rpaking c.anpoAents of the total resistance form"i;he conten-@ 'of q+apter A bibliography is given of' some reports pulillshed beiiweea 1924 and 1935. .

The hydrodynamics of marine alrcraft is presented in a general form and. the development and description of seaplanes, model .testing apparakus and'result8, dpami'a stability, and $@,pressure diatri. ._ . bution on planing surfaces are dSscus8ed. . .: . . ..,

Critical study o$-suggestioa of CIiarles E k 3 a d a R a m s to British Adniralty to adopt stgpped I n c l i n e d plane@as bbhape of hottam of ship6 with a view to biO'reasing speed. Suggestion was made to Admiralty in 1872 8pd h a s been since exmined theoretically and

. Theory of,skbmors; author produoes simple expression far reatstance; usiw thoory o f Lamb and Hoguer, he oap3res aotual wave eystem with theoretical; good agreement found for deep water but not eo good for elasllar; ccmqa.rison with Pavlenko theory.

The tw~ilmenelohaf. gliding of a semI-i@ini* plate otl t h e 6uxf'ace of a stream o f ' f i n i t e depth I s examined. -The lift L in terrms of the r a t i o D/H, wha:*.'e Ii is the depth of the atream a t inflnity upstream, and D is the height of the. trailing 'edge of t h e plate above the surface o f the stream, i a calculatedr..-In gsrtlcular I t ie fquntl that the trailing edge cannot be at a,heigbt of.more than 0 . 0 7 E approx3nately, above the upstream f l u i d surfaoe.. . . - .

..Author

63

HYDRODYEBAMICS

Suetentation

- Steady PLaning

In order to determlne t h e valuee of liftJ drag, and moment of a eubmerged flat plate, it ie rreceseary to deternine the mean relative retardation faotor and the ratio of the actual wetted length tu the length frm the step to the interaection of the undleturbed'wat,er.surfacs a8 a function of the velocity, angle of attack, and aspect ratio. Rather than t o atibapt a difficulttheoretical mlution, the t e s t results of S o t t o r f (abstract 8 2 )8 r e errtployed. and. the curve8 are presented; . The effect of Reynold8 number on the lift-drag ratio and. best trlm i s dZscuscled and I U u 5 %;rated graphically. The ccmputed reaistRnoe o w e of a seaplane ie given to show the contributions due t o hydrwtatic forces, friction, and form, The computed results are canpared with experimnt and the correlation l a omsidered good.

E w . Id., 1932, p. 849

The two-dimensioleal gliding of a plane p l a t e on a etrean o f infinite depth io discussed suathematPcaUy. A canplete solution for any angle of IncAdence of the p l a t e OA t h e stream is given, the reeulte being expreseed in terms of the length of-%he plate, The motion is supposed to be eteady and gravity is neglected. The p l a t e is taken a8 at rest, a d the stream ~ m p w e s on it BO that it leaves the t r a i l i n g edge wnocsthly and, forms a spiay a% the leading 8Qe. 'The. solution i e obtained by ~ 8 a n 8 &'$he SahwarzChrlstoffel tranefmmtion. In Wagnerts solutlm, the lift inoreases linearly with the epray thlclcnees, 6; in the preeont solution as 6 inoreaees frarp 0 to m., the lift incre&sest o a maximum and then deoreases t o the finite limiting value of the olaesiml. Raylelgh flow,

".The'lmpmentumpassed t o the dcwnwash is evaluated a8 the product of the mhmentum o f - t h e flcw i n the tramverse plane a t the step by the rate a t which such p@nes s l i d e off the step, S 1 8 eguatiorre a r e giqetr that permlt t h e uee of planing data t o evaluate empirically the maneaturn of the flow In the traneveree.plane a t the,step. On the basta of such studyr modifications of the general equations of' the prevlous theory is supplemented by substantial improvament in . t h e formula for the manenturn of t h e flow i n the plane element. T h i s improvement can be made because the flow in the plane i.8 indopendent of the flight-path angle, ..

Experimental data for planing, oblique impact, and v e r t i c a l drop are used to show that the aacuracy of t h e proposed theory is good.. Wagner's theory, which has been the most popular theory up

length, f i n i t e length of the, h u l l , dead rise, and t h e ela&icity of the hull bottam. The application of the results to practical problem is discussed and examplos are given.

. A qualitative eat9mattlm of t h e impact forces 011 a f3.yIn.gbost b u n . ie 5tternpted by prqceedZng in a manner similar t a that w e d by vw1 E L a m a a ' n (abstraot 93) A simplified c88e of a &dgdshaped body dropping v e r t i c s l l y into a wedge-ehaped wave and t B 6 n In still water has been coneiderel. The results of 8 congutation are cqnpared with experimental resulte. [Poor agreameat is obtained. ] . .

'

NACA RM No. L 7 J 3 . 4

76

.,

.I

.i.

77

.underway, the hull is supported above .the wahr by throe laddelrlike sets of hydrofoils., The hydrofoils are set at a dihedral angle so t h a t "reefing" or the variation of immersed area with depth of immersion is apooth and cantinuous. A fourth set of . hydrofoils s I mupted at t h e b o y t o prevent t h e bow frm dlv. 8nd to help. lift the hull a t low apeeds.. . The c r a f t r i d e s smoothls even at high speed i n .waves abdut ' i r feet high, The top' speed is ,. ' 2 about; 70 milee per h & . . . . .

. .. Immersed' vanes located on seaplanes and on o r i n the water'do not present improvements for take-off, and, in particular, theF increase drag in water and in a&. It would be possible to make.tham retractable during fllght, but these vanes are a l s o said to be s e n s i t i v e t o the phenca~enaof cavita.t;ion and to ma 'the risk of deteriwation upon encountering bodiea.floating between the two wa&es. Worley, however, la an advocate of this arrangement which, he guarantees, w o u l d constitute g r e a t progress in =rim aviation. -. I

Question of whether hydrodyknfc support bg lmmersed wings on or i n t h e w a t e r can improve take-of'f :of,eeaplaaes i s briefly'discussSa with quotations Fran a paper by B . Worley and brief references t o and 5llwtraticme of early inventions by Borlanini; ,Guidord, S t e m , and Pegm Dwrtng hydroplaning the floats of seaplanes fsret ris.ing higher out of the water, have furtliejf c a t a c t wfth t h e 'Water only on tho edge of the atep. To elwrrate this cbntact, B . Worley proposes . t o install immersed vanes under'the flmts. These wings o r vanes'would guarantee a. higher lift than a t fu'mished by %he floats, because on the f l o a t 4 l i f t i s due to pressure exerted OD the-bottan of the float while the immersed vane w i l l be stressed by a positive preesure on the bottam part and by a .negative preesure on the' upper part. It would also facilitate'landing..

This power reserve could be' reduced'if t l m angle- of incidence of the hydrofoils could be a l t e r e d ao 6s t o lift the boat at 8 lower speed. Apart frolg mechanical. dif Sicultles, this ihtroduces'.' the danger of cavitation.

From the shape of the power c m e s it appears that hydrofoil boats can only be jwtlfied if opexpted st maxfnnun speeds. A t intermediate speed8 the boat m a y t a b considerably more power than a normal boat. If, therefore, a large speed range is requimd, it i s essential to provMe some method of f o l a n g up the hydrofoilsurfaces

between lifti; resistance, and trimming moment in the planing condition is e'implified by the use of coefficients similar t o those used. i n aerodyasmics. This eimplification f o the ~ triming moment does not occur when the afterbody is wetted. The following e-vression for the Wt of the forebody In the planing ,condit$o$ with' t h e . . . . chine6 'wetted is derived:

L =

. 2

e V2b2($3d.: _.

0.65,

'.

&

570. Anon. t Bureau of AerQt1aUtiCt3Design No. 71 2nd A l t e r n a t i v e L i m e . Madel Bqerimente. Rep. No. 223, U S E M B , May 1929.Specific free-t+trSm a,nd fixed-trim resistance test8 and tests of the lon&tudinal and lateral hydrostatic stability were made i n the S . Experimenkl Model Basin. of a L - s i z e model Of 16 the second alternative hull and OriginaL auxiliary floats of the Bureau of Aeronautics deeign no. 71 flylng boat'. The results of . . t h e t e a t s are given i n graphical form. The hydrodynamic o h a c t e r i e t i c s of the model are ccqared w i t h those of the ,original and first alternative hulle (abstraot 579). The greater reSi8tanCe of the *second alternative hull i e ' cauaed by the fncrias'ed angles of dead r i s e and afterbody keel, .. . .'

Specific fbe-toltrim and fixed-trim reeiatanoe t e s t s and tests of the hydrostatio longitudinal and.lateral stability were made i n

. .. . , .^.

. NACA RM No. L7J1.4

84

86

boat. The data .were requested for use in the cconputatlon of longitudinal stabY.llty.derivatives. The results of the tecta are glven iq,the famn of curves of trixning mcment, draft,-and resistance plotted against speed. The results of hydrosMtic trmnIng4icsnent end draft teotle are also given. The a?ccuraCy of the drdt measyemnts .is.dlecussed., .

showed a decrease.in spray with increase in length of model; The spray oondition of the family of models with a greater dead rise w a s 8 8 satisfactory 88 the family of models with Lower dead rI88,' .The .results

Specific resistance and hydrostatic stabJlity t e e t s were made S Experimental ModeL.Basln of a model of a seaplane float. .with .varying depth of. etep, :Two. series of ccmfiguraticms were used; one i n which the dead rise was held constantj the other, i n which the dead r i e e was varied while the depth of' step a t the keel was held .cow&ant,. The height d the stempost,. aiXerbody. . ' keel .an&e, and dead. r i s e st-the s b r n p o a t were held constant While the..*qf?erb@y bottcan near: the step was warped .to form the found that a ,aha.llm etep was different d q t h s . . o f .step.. It beet a t o l w speeds, and a deep step was beet a t speeds where the tail w a s clearing and the.mcdel m a beginning to plane. A t high pl8ning. .speeds, too deep or too .sbllow a.step'waa undesirable. The . a p t D w u @e.pth, of e b , p yas, about 7 or 8 perc'mt of t h e bean. previous experience h a s shown that an.increas8b afterbody keel angle o r a decrease i n Length-beam r a t i o aUows the use of a shallower's t e p . .. . *. .. , .* . ..a t the. U,

Speirific he-to-trim ree'istance 'tests were made in Langley &alee mbdol of the. flat of the M B 1 seaplane, 4 to determine the effecte bf changing from a forebody with corpetant dead rise to one with a warped bottom obtained by fncreaelng the angle of dead rise towarde t h e bow. The mdel was In two parte: the bow mction, which camprieed about t w w t h l r d s of the forebody; and the .hain ~ e o t i o n ,which Included the afterbody and the a f t end of the forebody. Twa bar section6 were usedr orre with constant angle of dead rise and the other with a warped bottom. The effect on reeistancm o f the forebody w a r p i n gw a s negligible. A t o l w SpeedR the sgray of' the model with the warped forebody was higher than that of the model with owatant dead rise. (See also ab&mot 629.)I

NACA RM No, L'j'Jlk

' .

, In addition to the usual me8surenientls of.re8istance and trimming moment,' mba,eruramente were made of the length . o f the.planing bottam . ' i ,which wetted By the water. The .draft of tw forebody alone was measure$ using a lllethod which eliminated errors caueed by up-ahd, -. . d m aurgee of the water In the ,. , : *,w q E I .

tank.

'

The application of the data..bo the determiation of 8tEtbilfty

By considering t h e A;ladamental equations o f ' l i f t and resisWnce, expressions forthe maximwn resistance and the rerslstance during planing are developed for a . cylintlrical float seaplane w i t h a separate planing surfhoe placed under the floats,. These expressions can be used t o datermine the optimum area .. . . of the pla&ng * surface . .

"

NACA RM No. L 7 J 3 . 4

The rrpsistBIlce a t phiiryl'' spe'8d8 was a h W t Canf3tant and Was about one-fl9th of t h e . g r a m . weight; The trm i.ra8 low at high speeds A t speed8 .greater, than-hump s p e d the resistance in acceleL;gLted.mation a t a mean acceleration of ab-out 0.15g was about Q .percent l I leqs than t h a t $n steady m 0 t i . qwhen' t h e two sets of data yeqe, campared a t the .&%ne Fa% a@eemdnt was obtained . i n the. resietances a8 deteminbd bx the"5wa ~.t&th&s of meas-nt. when teed .a%the same trlm.the.'resi.E*nc&of t b f'ull-size seaplane,,was about 1 0 'percent greater th& that of the. mode&s. It is pointed out that t h i s difference in resi$t&nce ~ - not 8 neceeaarily ! , : due w h o l l y t o scale effect, but was influenced by t h e y a w i n g of the full-size seaplane due t o wind and %ide, and By the'fact that rivet headb; se&;and lap joints were n o t reproduced on t h e model. The effect of yaw on the resistance- of the -mobL I s shawn.'

630. Sedov, L. : Scale Effect and 0ptIwzt.n Relations for Sea Surface Planing. NACA TM No. 1097, 1947.Frau the general diraeneional and mecbaniual e w l a r i t y ,theory i t folloirs that a c a d i t i o n of steady motion o f a $iven shaped bottom on the ourface of water is determined. by aondimeneioaal parmeters. The various syetem~lof Independent parameters which are applied i n them3 and practice and i n spectal t e s t s are conaidered and t h e * i p t m e l a t f o n s ,and +itabiLity 8 8 p l a n i q char- ' aoterfetioa are determ$ned.. I n stuQing s a a b e f f e c t on the &lie of' the Prandtl formula for t h e f r i c t i o n , c o e f f i c i e n t for a turbulent boundary layer, the order. of magnitude is @ e n .of the error i n applying the &el data to male,in the case of a single-etep bottcan. For . a bottcan of c a p l i c a t e d sbapo it is e h m how t o h e t e s t data of t h e hydrodymmiu obtain,by a - 1 ~ computation frm t characterieticg for one speed . w i t h vaxious lw$s or OF load with various a p e d ~ good p approximation of t h e hydr-c characteri s t i c s f o r a dlggerent speea or lcad. The extrapolation of the uurve of resiatance against speed for .large speede, inacceesible . in tank t e s t s or,.for other loads'which were not tested is thereby a t a obtained by canputation are i n good agreement possible. The d p t i n n u n trim angle with the t e s t results. Problem regarding the o or the optimwn width i n the case of planlng of a flat plate are oonsidered frcm.the point of view of t h e minfmwn resistance f o r a given planlng .speed and load on the water.. .'EOY.~$BS and graph are given for the o p m i tu m value of the planing'coefficient and the correaponding values of the trlm.angle and width o f ' %he flat plate.

sour

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f i l l , .

. .. L :. The reauI&e .are given of the investigation of a float with a longitudipa3, step which is'extremely high, ccmprsd with the DVL, single:float of the 3 ,family (2'jo angle of dead r i s e ) . As a result of these teets, which confirm tho rosults of provious,$eeta with o l w and with medium high steps i n the planing surface.aiia i n the front par'b.of the.float6, any longitudina&-stepsm a t be eonsidered'a8. unsuitable.I -

removed f r o n tho tail extension and chines added the full length.. o f the M i l extension, the chine f3are renoved frcan the afterbqdy, and the.dead.rise increased on the forward part of' the t a i 4 exteneion. A few tests were made with the ventilation ducts closed in . . order t a determine the effect . . of ventilation?"

The"epecific. reeietance t e s t s described in abstract 178 were checked a t a water depth of 6 feet and extend,& to include eeveral modifications of the flat models. The atop was moved a f t In both NACA model 106 and hlACA model 107, and. the curvature of th6 flutes on' -&"bottom wag decreased: A n aft movement of the s t e p increased the depth of atep end length of forebody'and decreased t h e length of the afterbody; ..,I.I .

The resis-tame of the model was r e l a t 1 k . y high, both with and w5thout side floats. The best trim had low values throughout the .range qf speeds a t whlch the.mode2 was teated. . . . A 'c-asnpakon of the te& aata with and without' th;s s i d e fldats show6 $hq following:, t h e s5de floats carry about 'me-third of the i w d on 6 water at hump speed, the h u m p resistance l e ,lower.with the .side floats than without them, and t h e resistance hump occurs -. , a t .a-.,lower speed w$t-h the aide t&x3ts than without them:. a' A ,

75 t o more than 100 percent greater reeistance near get-sway. It should be noted, .however, that in an actual application the centerI .

of ,gravity of the. planing-tail hull would have to be located a f t . : of %he s t e p i n .order to obtain the red9ction in r e s i s t a n c e a t t b hmp speed.Decreasing t h e width o f ! the afterbody increased t h e r86iSIXikroe and trim at hump speed, decreased 'the t r i m m i n g mcrments required% olx~in best trim, and moved forward the location of the center .of gravity required to give best $rim a t the hump speed. Increasing the le&h of the afterbody deoreaaed the resistance and increaseit the trlm over almost the whole ape& range and .mbved a f t the 1 + a , tion of the cent-* of gravity reauired t o obtain best trim a t the hump speed. Tapering the.plan f a r m of the afterbody reduced the resistance over the lower half of the speed range and had little" '

In predicting the resistance of a seaplane fram the resuitfl' of model tests, the e f f e c t of Reynolds-numberon the f r i c t f o a a l

resfstancle 5a ctustcagarfly neglected. A correlation of t3XiStiw information on the frictional reefstance of planing ~ W a c 0 s and modelsl of seaplane flaate show8 that, when no meane &re taken t o . control the boundary layer, it could.be lamlnsr, turbulent wZth laminar approach, or fuUy turbulent at Reynolds numbers up t o about LO7. 'Tests were made in the Stevens tank of a model with and without a strut tared in the water ahead. of the model. Struts &f. various sizes a t variou-e dietances ahead of the model were usad. ' T h e etrut tonded to make %he boundary l a y e r completely turbulent# and =de the epmy and wake of the model resemble those of a . . e l z e hull more cloflely.'

Steady Lqngitudilaal ~ o r c e e ajnd Mpe.ntS

- Resistance

It was found that the resistance of the Sull-eize flying boat was the 881138 as the resistance of the models a t a medium p l a n i x speed, was lees then th&tof the models at lower speeds, and wassubstantially greater t h m t h a t of the models a t high planing speeds. Previous ccpn.parisons between the iwvistances of f u l l - s i z e seaplanes and models have,shown the game trend, which may not be entirely caused by scale effect, but may be partly attributable t o the efrects of r i v e t heads and Lap joints on the fuU-Srize seaplanes.

F u l l scale take-off and landing t e s t a ware made of t h e N and Dornier Wal Flying boats to determine whether the water resistance, trim, draft, and hwnp speed a s measured fri tank experiments a r e i n agreement,with fullrElcale conditions, Motion gictures were taken of the take-offs and landings and data were taken directly frcaa the film. The resistance calcubted fram

R =T

-E a6

-D

for take-off

and

where R ls'the resistance, 11 I s the thrmst, W is the weight gf the seaplane, . g is theacceleration of gravity, a - I s the;' longitudinal acoeleratim, and D 5 . 6 the a i r d r a g. . . The data a r e presellted i n tables and Ir! curves.

Th8 previously employed method of extrapolating the t o t a l

resistance to fW.1 eize with X3

5s the model scale

. _.. The i n f o a t i o n given i n t h i s report is su%&ntially' the '& as that reported i n abstract 675.r

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2. A f l m t navigating i n the system, Qf divergente of a generating float, these divergents being reflected fram fixed walls s o . a s . t o form a new,divergent system a t a point distant fran the generating f l o a t. .'

3. A 'float navigating in the

flystam of divergentfl oftwo

The experiments EhoW th&t it . i s p08Eible t o annul the diu'ec2 tow.ing resTstance by p l a c i n g t h e float 'in.a s u i t a b l e a r t i f i c i a l f i e l d of waves, and that the interference'between divergents are as important as between transverse8, the l a t t e r having hitherto been taken as t h e ' e o l e basie f o r explaining the variations of resistancci ' a t ,con&nt speed observed, on.floa.t;e with'a'variable cylindrical

.-

portion.

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Sci. Abstr., 1926, abstr. 1220

Wichsll*sexpression for wave resistance is quoted and the . physical assumptions on .which:it is .based are recapitulated. A ' nondimensional resistance coefficient is defined, and i t e values, when plotted against a. norqlimensional velocity coefficient, show marked oscillations. . ObserVed..valuesplotted ,on the- same- scale for cnmparison shaw.much less marked oscillations. The center of pressure and distribution of preasure on a hydropane surface are also discussed. . .',L '

Tests were made in Langley tank no. 3. of a &:-size model of a

PBY-type outbosrd float and several modifications t o determine whether the modifications wmld effect an increase in the hydrodynamic l i f t of the float. It was found t h a t when tho model of t h e basic fomn was immersed a t certain ~peeds, it would fail t o emerge when the load wae removed and would h ~ v e t o be l i f t e d out. It was elso found t h a t the type of s t r u t used t o support the model influenced this hyeteroeie effect that was obeerved on the float to 8, conelderable degree.

General increasee In the hydrodynamic l i f t were obtained by the addition of horizontal fins t o t h e mcdel, by modifying the bar,. .

NACA

RM No. LTJl4. . . " .

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133

by adding a s t e p t o the bottnm, and by providing hydrofoils beneath the model.

Unsteady Longitudinal Forces Rzld Moinents

Rough-water a c c e p w c e t r i a l s were +de with .a H a l l . 3n?TBH-2 twin-float seaplane by the-Experimental Divisiozi, Operations Department of the IWrpton Road6 Naval A i r Station. puring these trials, records were obtained of the accelerati%s.and the dietribution of the water loads on the forebaliee of the floats. Maximum water pressures we- recordod near the bow and pressure histories were obtained over the remaining portions of the forebodfos

Take-offs and landings i n rough seas were made with a

Be 42 seaplano,.and the stresses in the f l o a t gear weremeasured. In the first t e s t series t h e gear was directly connected with thefloat; In the second series a shock-absorb343 amngemnt waaintroduced between the gear and the flea$. Ths etresms observed in both.casee were campared. By the introduction of spring arrangement between the f l o a t and the gear, the usually irrelevant.tension etresses were increased, but the stresees i n cc~llpreseion were decreased by an average of 16 percent. Because of the disturbances of t h e sea, the measursd valuae showed so great a diepereal that the indicated values for t h e decrease of the contpreasion stresses a r e not very accurate. The themy gives approximately the eame results. Author

MACA RM Bo. 27514

Stratn meaauremexlte a t . m f f and h n d i n g were carried out. The e v a h a t l o n 09 the msasuremente of the reliability of the construction are given. The character of the b a l i n g shock forces involved,VU be di6oweed in a later repart. Author

Canputations a r e mde t o g a i n a conception of the arder of magnitude of the path of bodies with various head forms. The computations a r e based on result8 of the inveettgations of Wagner and Schmieden and a r e campared with measurements of-the penetration resiatance by Watanabe and Ma jer. Author

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HXDRODYNAMICS-&

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:. . .'. Unsteady Longitudinal Forces and Mosnents

The questions arieing .Is,the course of the averaging of the t e a t rosults a r e treated i n ' iietiil; ~-uggeations are made for sizuplificationa of such measurements.and evaluations. Author

Meaaurements .were taken of.the longitudinal and normal accelerations (with respect t o body Sxes) m d the water pressure8 on the forobody of the h u l l of the Grummah J2F-1 amphibian during roughwater acceptance t r i a l 8 in t h e vicinity of the H8mpton Roads Naval A S r Station. A normal acceleration of 4.28 accapanied by a Longitudinal deceleration of 1.5% was encountered i n a landon a sea with mves about 4 f e e t , high aud a head wind of about 18 knots D u r i n g this landing a sWucfxra1 f a l l u r g occurred i n the iorebodg despite the reinforoemerit, of the,huU. by s i x longitudinal stiffeners. After further reinf'orcament . . of t h e forebody bg replacing the L-inch * . 32 hull covering w i t h k-inch. coverLng, the amphibian succ,essfully

16

withstood a series of test8 wherein a -no&l.acceleZ'ation of' 3.88 and a longitudinal deceleration of 0 . 7 % were encountored'. A ccmprlson of the water pressures and the acceleration data showed that both $he positive and the negative pressure must be considwed. In order t o realize a r o u g h estimat1on.of the e f f e c t of the loads on the whole amphibfan.. ...'

The pitching acceleratbns were ccrmputed from the reeponeee of two nixma1 accelerameters and agree very well with the value8 recorded directly by ~n expor'wntal a a c c e b r w t e r developed at These l a t t e r vabuee, however, were based c m a laboratory C8llbrf3tioA a t 0 . 7 7 C Y O h pep 8Woxld. ,Since the PItChlnfS 8CCel0mtid u r i q landing aocwred a t a frequency of 8 cycles per second, a consideration of the m i c characteristics of thls Instrument lndlcates that its readlngiEl are t o oo l w by approx3mitely 14 percent* Pram %hebe facts, it i s eonsidered that the pitching accelerations caput& fraa the n o r r r s a l accelerations.are sleo too o l w by approxi..ma*elythls a m o u n t , due, preeumably, to bending of the fuseLage.

When the bclw was immersed simultaneously w i t h the step, the . pressures a t the baw were the"+ i ~or ' greater than those at' the step. Large angular-and linear ccmgoriente of aoceleratibn occurred simultaneously, both when t h o Impact occurred over the whole forebody bottan an& when the 3Itpact occurred. primarily at the bar. The local. failure of the huLl near the bow As probabJy caused .by a .. high average preeeure extending. over a ,l~mge and aesociated with a peak presauro of about the ' t i y n m l o preesure . (about 50 pounds persquare inch). The failure of the eqine'mo\lnte was attribute'd to the effect of a large angular acceleration supeqosed upon t h a t -of a moderately Large linear accel&att& at the ceater of gravity. From the nature of the i q a c t i n the'.severe land-, it is considered that l a d e i n ~ o e e din rougher 'wa.t;er would not have been those 'imposed. i n this landing. greater .than . ... . . . ,.. *TU. ,Mewee, E . ' : Seef&igkeit einee Zweiech&immerPlugzeugs ...{.I Teilbericht: Stosel&aftb'estfmnungen fm Schw3brmwerk f. -. . (Seaworthinese of a T w i n 4 l e t Seaplaae. Partial Report:: ' ' -,-\"Determin&tion of D y m d c Loads i n the Gear) . . .FloWtion . .. . ; ' ' : E 5 No. 339, Z.W.B. . . ' . . . . . .' a r e a

The l i a b i l i t y of eeaplane floats and hulls to failure a8 a r e s u l t of the Impact of landing and high-speed taxying i n a, rough 8ea I s dlscuesed. The hulls deeigneb bx 'Linton Hops (abstr8Gt 451) were of flexible construction t o abeorb lan8$ng shocke. Teste were made during W o r l d W a r I by the Britieh of a hull with the forebody planing bottam hinged t o the h u l l a t the bow and supported by cnmpresalon eprlnge near the step. Tlie reaulte were not entirely eatisfactory. A mare aatiafactorf hull shock absorber was Ln the form of a seriea of individual cantilever slats each extendiw . acrose the hull and faa-bened t o t h e hull a t the leading edges o f the slate.

' The strains 'in t h e float gear appearing on several models a t take-of'f and laqding i n various wave conditions were measured. The s t r a i n meaauremente form a part of a program to eetablieh new loading criterloqs. The test reeults are canpiled i n table8 and ccmgared w5th calculated values. Author

Take-offa and landinge of a &tan flying 'boat were made on the Potenitzar W4ek near Travanbde, in the Bay of LGbeck, and i n the North Soa, and the e.treese8 at varioue places i n the structure w6r6 maaswed.,, -Onlong wavee"(ef3timated rOu@;hneS8 of the 1 3 - 3)* the eaf'e load limit8 reached in tha weakest member6 were determined by the mea'surfx instruments. On short, steep waves (estlmated rougbees of the sea 21, one part of the s t r u t between the keel and. exine support of the fron-b transveree frame exceeded the safe .. load 1mt. Author

determhed on the basis of the arrangement and the dimensions of the float undercarriage. The impact forces were eubdivided i n t o symmetrical, asynanetrical, and l a t e r a l fmpmta. The i n e r t i a forces which are created by the iiupact and are derive& f r a m the airpune, which is asamed to be rigid, and the l i f t and weight forces of the condition of f l i g h t are taken into .co(nsi&eratim. I n the d i a g r F ? : , t h e impaat force13 for a factor,of aafety of 1.55 and the influence likes .for the atrut stresses .created By a'i z n i t ' lmpact force are plotted agafnst the le-h of .the float. Stlength and , Author calculation values are tabulated,.I.

The data subetawbiates and extende t h a w obtained with the

P2Y-3 @betracts732 and 733). The impact loadsincreased with the

square of the landing speed and increased rapidly with 'trim. There appear8 to be l i t t l e jus%ificationfor the present reduction of design loads towards the bow and Chinee. A deep, sharp bar might. permit such reduction i n bottcm loads at the bow and 3reep.th.e angular acceleratione d m to safe valuee.

Although sidedoad conditions are required for landplanes and f o r float seaplanes, thore are no such requirements for flylng boats. In a L a n d i n g wfth side d r i f t , a Lateral water l a d is b u i l t up on the hull b o t . t a m or lower portion of the h u l l side t h a t imposes a rolling accelemtion on'the azrplane. 'The loads s e t up. &y be . c r i t i c a l for bulkheads OT wing fittings.By aesuming tbt the prebsyre'o b prfe side of keel .$s' the same 8s in t h e symmetrical s t e p l a n d i n g oonditicn while that on t h e other side is reduoed to on&laaI.f' the steplanding value and 0 by assuming a dead-rise angle of 22A it was found %hatthe t o t a l

*727. Sydar, J. : Beanspruchun&gmessm.gen an einem 3'lugboot b e i

The pressure on t h e bottcan of the hull and the tresses ia fndividual parts of a flying boat were measured d u r m take"; and landon rough sea. The measurement gives magnitude and distribution of t h e pressure on the bottom of the boat. B"r0pn these measuremente,coaclusions can be drawn a8 to t h e safety of the whole construction, and tAe basis for construction specificatione."

A number of hulls were testad in' tho Stevens T o w & Ta& and the spray p a t t e d recorded (me abetract ,249) The reeulte ,cover a range of epeeds and .wter loade.'en'coiyitered during the pre-hump tax1 r G and are applicable 'to any boat h u h similar to t h e f i v ementioned.'

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The d a h are analyzed t o determine the 'poaslblllty of 'eprag pattern prediotion. A nondimensional method 18 evolved which i e eatiefaotory for this purpoee. Examplee,, shmlng the application o f the .metho3 to a number of hulls, are iricluded. A chart ehciws a metho&.whereby.satisfactory propeller clearance may . . be estimted.

Longitudinal Stability Under W a y

E Y D m m A M I c s

and at the Glenn L. Martin C a p a n y (abstract 748) Differences between t h e methods are shown and dIeceg.ed. Cornlation of the a e r imposeibie 'uzi.fi'i5-.sx3mml.on of..t;he two sets of formulas w G l e n n L. Martin derivation resulted in a e e t of formulas l i k e the New Yorfr;-.:Unipsrslty set except for the vertical velocity, w, d e r i v a t i v e s . The final agreement between the two method6 of amlysis indicated the preference for revised New York University formulae which have t h e w derivative8 corrected for apparent draft change.'

A MetBiod for QutilL%ative Boxpolsing A n q l y ' a i 8 by Meana of Center of Presoure Variations. Rep. No. XI.&, GIN, OCt I 2 9 1939.

. ..NACA RM No. L7JIk

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161

To elucidate t h e pdypoising problem a mathematical investigation was attempted and the steps of t h i s investigation are outlines, The theoretical work indicated: that a variation o f t h e horizontal ccanponent 02 a:'seappu3e's velocity had negligible effect on the s t a b i l i t y "criteria,' a n d : hence t h e Inetabilfty of porpoising can be ascribed to the interaction of the vertical $rid pitc.hlq motiona. The work also shared the aecesaity in m b d e l t e s t s of using true dynamic m o d e l s . . . .. .

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.,.

(See

also abstracts 754, 780, 794, and 795.)

NACA I M . No.

Longitudinal Stability Under Way

Stability Characteristics.

The r e s u l t s o f ' te8ta..of th? t i p f l a s t showed tfJat, each of the three models with increased length produced greater dynamic l i f t ' than the basic model. The moaification which had increased width mar the stern produced the greatest dynamic lift. L i t t l e change in hydrostatic l i f t was noted between the mcdffications.

. . ,all .forme of in&b%litg associated with high tr-. are func- . . t i o n s of t h e afterbody. The jet-pmp action. of the wake fkm the forebody flowing below t h e af'tarbody induces ,a region of a l w pres- . sure. on the afterbody -.tho step t o the point of impact of the roach. This o l w pressure is.gwt;lallynullified by a i r flowing in f r a the sides of the step, and :additionaL'n&Ltfication can be obtajned .by increasing the depth of .the s t e p or by .adding ventila. , .. tion ducts in the aftextbody nearthe s t e p . ..' a

Information on ,the sklpping characteristics :of a flying boat and the ef$ect;a o f ' various modifica.t;iona w e readily obtained f'ram landing t e s t e of a 0 model in a t a w i n g t a n k . The ef'fecte on tako-off a t a b i l i t y of modifioations made t o improve ,landing s t a b i l i t y should also be investigated. -

The upper trim limite of 6tabilitr occurred.at Laser speed8 than wlthout power. This change l e similar to that obtained with a deorease i n load on the water.'

A t ,fo&rd.pmitiona of the 'center of gravity the model w88 generatly etable on a l u d a l gw i t h or without parer. Skipping that occurred during landings with the center of -&ravity a f t of 36 percent mean aeradynanic chord was reduced when Icmdlnga were made with power.$ This difference in landing s t a b i l i t y was small and m y be associated with the decreaee In lading speed t h a t Le obtained with power

. ,qhich ,@Fee .with. speed above,.the. s-$alliqspeed. The behavior

,j$+.

'

of pod&. w6e greatly improyed by Increasing the .ste-p depth, . ventiLEtt2rig the step near the center line of the aftmbody, or fitting a 3 0 swa~law-tafl step. .<. dbs&aa'tio& of.the preesure just aft of ti?e utep ware made using. a multimanameter. It wa6 found that a ~nall negstive preosure exlets a f t of t h e step. The 'negative pres&& increased t i t h the increase. i n speed and'was greater d u & i n g Forpoising and landing a$ high:trhs than a t " 1 m trims. The negative pressure on the .@.fterbodyfe considered to be an. important Muse of 1 n a t a b i l i t y . a t" "

aleo'abetracts 5Q5, 736, 746, .and 747.)

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The orash of a Sikor8ky & 2 B flying bcat during a night l a n d i n g In San Juan Harbor, Puerto Rico waa inveet2gated -bythe Civil Aeronautics Baard. I t w88 found t h a t the oaptain landed the flyipg boat in ap unduly nose-low attitude with a sllght drift to port. Alrsmt lnnaediately after contact, the,aircraft swerved violently t o the right and broke anto eeveralwjor s e c t i w . The water was emooth and there wa8 a bright mom almost direotly over" head, tending to leeaen depth perceptfoa and detem5natloa of

sideways motion.

808. Milliken, W. I ? , with euppleme,qjaq.remarke by R Bush:.

Report of Dpmnic Y&w Tee3k, ModelA%., 2 9 4 0 .

x p B B 1 . .

BAC Rep. No,

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General

810. Webster, W. W.,

A n analysis is made of the .cmpu%edaerodynamic perforinances' of groups of hypothetics1 flying and weights.,of ccaponeqt pr%s boats, haw of which are biplanes and half'monoplanes, the other primary variable6 being engine power and etalling speea. A l l boats i n each group are gecgnetricam similar. A summary cmpariion 1s made on the basis of:..

The appreciable interference effect on t h o 1"S-tof a seaplane h o surface o f the sea, and which according produced by flying near t to experiments carried out a t Felixstawe may produce 8.10Fercent x j m u m l i f t cannot be eatisfactorily explained-by increase in the m the .ordinary vortex theory, In t h i s paper a mathamtical analyblis i-s',made oP'the problem of calculating the l i f t of a f l a t plate * . . placed i n a ' twcF-dimeneional contfnuous -stream of fluid which- ie bounded br a free surface~oht h e Lower side of the.p"b, aesuming various values f o r the angle of attack of the plate and for t h e distance of t h e p l a t e f r o m the free surface, It is sham that for praoticelly important W l e s s f attack, such -a@ loo o r , ' 5 l the . I f f % i o increased ky a ' few percent 'due t o the.presence of the free emface when the distance of the'plate frm I t-is, of ..the 883118 order of magnitude as the breadth of t h e plate. -Yie surface of t h e sea being cclnsidered 18a free ewfkce, by aeswning t h e water a t rest and neglecting gravity, the theoretical results are applied t o the case of a seapplane t g q y i n g over the eea .s.wf'ace, .and it is shown that for an angle of attack of about 1 5 ' 'the m a x l m m lift may be expected to be increased by about 6 percent .when the .-distance of t h e w i n g frm the surface ie of the &er.of t h e breadth of the Wm3* . ..', .

Tests were made of a L - s i z e m o d e l of "the N3N-3 landplane and

+&

(See

abstracts 468, 601, 735, and 826. )

202

Reeearch.-Wind&unnel. tests were mads a t t h e maticma1 Physical

_7_

Laboratory of

m c d e l e of the three seaplanes and many of,their

NACA RM No.

L7J14

"

- .

AwODYI?AMICS

Force6 and Mcmnts on Hulls and Plats Wlnd-tUnnel investigations of a '-size

model of the

S ; 6 3 were

made a t the National Physical Laboratory. The investlgations Consisted of: ' t e s t e of variaua floats in,an e f f o r t to decrease the a i r drag; t e s t e - of the a i r fl& inside the wings for additional. cooling of the wing radiatws;:. tCist8 :of varima prgpellers; teats o f ' t h e caanplete model with-an&without gn operating propeller; and tsets of the directional stability of the model without floats i n the presence of a ground board .simuFting the sea during take-off A drag coefficient based on voLume2 was found t o provide 8 basis for c a p a r i s o n of the air.drag .of .varioue floats.. . . ,

The turning of high+peed a i r c r a f t aroupd pylons was Investi- .. gated by t e s t s ,of the raoing.ssaplanes. TeRts of maximum Bpeed, take-off time, and static thrust.of the seaplanes f i t t e d wfeh prop e l l e r s of varying pitchdiameter ratios were made;. The flying and water handling characteristics of the seaplanes and the medical aspects of high-speed Tlyin8:az-e discussed,. A description of t h e contest, and the establishment of.a world's record maxiiui epeed .. of 407.5 miles per hour, which t,Qok place near Portsmouth, England; ' is given. .. . ,

With knowledge of the seaplane model, caJsulated

The e f f e c t of the flying boat oa t h e a e r m c Ch3kiAeristics of the tail surfaces.fs resolved into caponents. The part which each canponent h a s i n the total effect of t h e flying boat $6 determined. The maximum a8 Well a6 the average effect which each h e tail surfaces i a evaluated, l3mpirica.t f m u l a s factor has on t are de;ritl,rped which permit oalcu3+?tion of the total effwt of t h e flyi3g boqt 0 x 1 the C , and Cy values of the tail oUrPaces and thus to trace the C, ana -,% curve^ of the tail surfaces in a c t u a l cond;tia!s. A thepr4tical analysis is =de of t h e structure of the aer&Jrlactmic shadow thrown by the w l n g an the tail, g i v i w results closely corresponding to the experimental cmclusion.Airc.

S p i c i a l equations for the ideal. tv&%&o&l air l i f t and m-nt of a plane airfoil which %oucWs,tb-?wp@ with its t r a f l i n g edge that were developed by Xtwyler are checked By using:general.., 4 .. . ... .. . ... :.

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veLwity

211

AERODYNAMXCS

Forcbs and Mcanents

011

Hulls and Floats

Wind.-tunnel t e s t 8 0 x 1 a famfly of shapes showed that the a i r drag of a conventional.flying4mat hull wSth a tmnsverse second . step was 50 percent greater t h a n that of a symmetrical streamline body of the same fineness r a t i o . Second-step fairings were found t o give satisfactory hydrOapa~~Lc chnracteristics and permit a . reduotlon of about 9. percent in a i r -drag. Mail.1-step f'airiqs reduce the drag.by over 10 percent but unless retracted m y give unsatisfactory resistance characteristics. The possibility of u s i n g a i r j e t s i n place of discontjauities in t h e planing bottcgn is suggested. T i p floats were found t o be better aerodynamically than stub w f q a . L q i t u d i m i l stabili%yis mentimed and a few .generalrules relatingge~m&r.ical&ape to position of t r i m limits 00 s 9 b i l i t y are given. 3hpac.t; t e s t s are briefly noted i n which von I l a d n t s impact formula (abstract 93) was substantiated. Menti.cn is made of a wave recorder. [Pre'cis of p p e r read at a . meeting of the Lilienthal Qesellschaft in Berlin. See also Jahrb. 1938 der deutschen Luftfahrtforschung (supp. vol. ),

The r e s u l t s of six-ccqonent measurements on a model of the flyins boat "Dornior WaL" are given. The t m t s w e r e =&e in t h e wind tunnel over a plate representing the w a t e r surface at angles of yaw frm' 0 t o 360 and at various trfms and angles of keel. Several tests were mads ,to determine t h e e f f e c t of rudder and ailerons. The results are discussed and capared with the reeulte of similar t e s t a on a model of a biplane-flcatplme (abstract 341) Author 831. Irving,, E . B , and Batson, A: S. : Spinning Eqerlmsnta and Calculations on a Model of the Fairey I I I F Seaplane with Special Reference t o the Effect of Bleats, Tallplane Modifications, Differential and Float- Ailerons and "Interceptors .I1 R. & M. No. 1356, British ARC, 1930. .. .. Teats of a model of the &ire7 IIl3 seaplane were made in the "-foot wind t m l o f t h e National Physical Laboratory to

832. McKee, John W.,

Pttch teste were made in the Langley 7- by Lo-foot wind tunnel of a model of the xsc-1 float seaplane t o determine the 5 ' l r n i t u d i n a l stability- and control characteristics and t h e effects of various modelmodiflcationa made t o improve the longitudinal s t a b i l i t y ; T h e reerults indicated t b t the nodel w e s t a t i c a U y longitudinally stable, Eltick fixed*and stick fme, for the clean n the .dirty condition with and without power. The original model I condition became w t a b l d a t high lift coefficients when parer. wa0 applled. Tee'te of the separated main float in the presence of t h e re& of the model indictated that, at ' I & angles of attack, t h ' e ' applibatiom of parer caueed the float t o contribute only a alightly more unstable moment. A t high angles of attack, however, the float contributed 8 large des-t;abiliei& mameat. By retracting the,inboard B S C t i O n B of the slat &he s t a b i U % y 2 m e 'improved a t the expense of a reduction of C h x , propel4er. wir@nillfx, of about 0.5 but without appreciable reductiW<of with power. The a c t d i t i o n of large end plates . & n d more a r m t o t h e hc&ontal tail. g r e a t l y improved the s t a t i c longitudinal stabflAtx, 8 y conditioa,''

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2 3 . 4

HACA RM Bo.

L7n4

NACA RM No. LTJ14

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211

*844. Brice, David:

'. -

Flying'.&

.B&t.

Aero&utics, Dec. 1944,

PP. 47-9.

It is noted that when'a flying boat is on t h e water it is virtually a marine v e s s e l and themfore subject to wtural and maa-made l a w s of the sea. The crperatip of t k ; e flylhg.boat under these conditions IS discussed. Sections 00 t h e artich'refer t o moorings, t a g i n g , take-off, l a n d i n g , and m o o r i n g procedure after

Dlffsmncee in the handling characterlstfce of seaplanes and landplanee are indicated. The epeciallzed techniques requiredafor operation of a seaplane during the taxying, Wsdf, and landing etagee aro deecribed briefly.

Aero. Eng. Rev., Sept. 1945, p. 73

221

,222

NACA

RM No.. L7J14

864. Anon.:

Flying-Boat Modringii.

.3r 1943s PP- 474475.

.,

Flight,' vol. XLVII, '. .'

n 'o . 1897,

A method of docking flying boats, devised by Saunders-Roe, &$d., -3sdescribed. 'Opposit% 5he coveeed laangabdock into which , . the flying host is t o be ,hEiuled there I s a breakwater, parall& t o the grant of the J m n g a r and-feci%, it. Between the. breakwatw and the baGk wall of the hangar there i s , a n endlees cable, the up2er . mn of which i s supported on or n&r. the water surf&ce by small .* buoys. St.ops are spaced -about 10 f e e t apart along the cable. A ' special hook on the bow of the fl.ying'.b&t engages the cqbi,e, w$ich, i s used for hauling .the' flying'. b d s t I d and ' g u t of the h a e a r . A . . l i n e fran the breakwater t o the stern .of the flying . b o t. i s 'used fo .a control the.headinig of the f l y i n g boat. , . . _ _ . . .. .

brfnging ashore,. and handling

flying boats on ground.

OPERATION Seaplane Bases

Bov. 3 0 , J . 9 4 5 , pp. 642, 643.

,

,. .

Details are given of a suggested g u n to construct c0mbinat;Ion landing f a c i l i t i e s for"landplanee end flying boat8 a t Largetone Harbour, Portmouth, The scheme harj been prepared for t h e e etagee of develofpment, the first af which enccPnpaeses the enlargement of the. exlsting airport t o accamodate Dakota-type a i r c r a f t , the d r e d g i q o f - a n adjacent mooriw basin, and the prov5sion of three. water ruinrays over 1 mile' i n length and with a low w a t e r dep%h-'of: 1 0 feet. Temporary landing elips and terminal building8 would%'be. erected close t o the main road and e l e c t r i c railway to ando on. In t h e second lstage of developanent, the three water runways would be nearly doubled in length and a new land W e e created on.reclaimed.land. The erection of barriers acrose the two sea i n l e t s i~l provided t o insure a oomtant water level thronghout the harbor, with a minlmum low water depth o f ' Pj feet In three runways and.."12 feet i n the mooriw baain and t a x i channela. In the third atage the water runways would- be. widened and extended by further dredging, and ''f1Utf would be provided t o extend the reclaimed area i n order to provide for a duplicate e e t of parallel m w a y e for the landplanes. .If'rieceesary, a water rmnxay 18,000 f e e t long would be dredged i n the direutian of the prevailing w i n d . . .

I t i s s w e s t e d to represent the measured 888 roughness by frequency distribution cwves of wave height, wave f'requency, and wave steepness. The numerical evaluation and ccmparison of the sea roughness is made by the uae of ooefficfents that can be read fram the frequency cwttee. Author

OPERATION

Seaways'

The r e s u l t s of the measuremento and observations made f'rcan the ligh"8hip Fehmamibelt (Baltic Sea) are given and c a p r e d with each other. Based on t h e r e s u l t s of these measurements t h e frequency c m e s of first and eecond kind f o r the mve-heights and of the wave-lengths are given'for fourdeek periods i n October and Xovember 1936. For t h e years 1937 and, 1938 only observations are used for the deteminatlon of the f'requenoies of t h e wave heights and gf the sea roughnesses. Finally, the connectian between wave height and sea roughness i s established. Author

A seriee of parallel pipee c a r r y i n g cmpressed a i r are submerged t o a depth of s a w 3 0 feet beneath the surface of t h e water. Each pipe, 4 inchos in diameter, s r i perforated wlth s m a l l holes several inches apart. When a wav0 passes over the apparatus, the jets of cnmpressed a i r rebaaed through t h e perforation8 a r e stated to smooth the water surface.

With the use of strong 'rcolumz18'~of canpressed a i r It is contended t h a t a large wavo could be cnmpletely levelled.

'Pests with a "wavGbreaker" in t h e harbor of Sebaatopol (Black Sea) are reported t o have shown that waves 3 or 4 feet i n height could be reduced i n f o r o e and height by 4.0 percent. The wave crests were entirely smoothed aut.

ESee alflo z .V.D .f

., vol,

77, -3dJ 8, 1933,

Jour. R.A.S.,dl

.: 755.]..

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.'

Oct. 193k, p. 850. Vaeca

''

.. Photographe and ccmgrehensive diagrams show t h e bridg+type , ..i. .. towing carriage of the Guidonia towing basin. The apparatuet, weighing only 6000 kilograms ( 13,200 lb), uses 100 horsepower a t i t e lpaximum apeed of 20 meters p e r second ( 6 6 f%/sec). Quick starting i s given by an electromechanical device, which also gives a Varying range of speeds. Pneumetic tires have been preferred t o metal or .solid rubber, but emergency metal wheel8 came into operat i o n In arise of a tire-burst or puncture. The car can be entered from either side and is surrounded by an external catwalk t o f a c i l i t a t e observation while i n motion. ,. , .I

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240

'

RESEmcflEquipment

o s t accurate if 8 The d i r e c t method is l i k e l y to prove the m eatisfactory mechanism ca.n be designed. With. the indirect method, same important errors can arise fram different sources, and a high order of accuracy m u s t be maintained in c e r t s i n recording instruments. A t b s i a e t e r i s eeaential for b indlrect method. . . use . with t

"907. Behrens, W. : Eln Verfahren zur Messune; &e31 beaufschlagten

In order to w e data on landing impact fol. t h e pmdlction of impact forces, I t ia neoeseary to datermine aeveral needed. values eqerlmentally. Up t'o now the theoqy always assumed a constant "hltting length" during the -reion a t landing. In this case there would be a pressure wave parallel to the keel line, and running f r a the keel to the water line. Actually the ,wave aleo runs f.Ww&r& from the step, and hence there will be a resultant, oblique pressure,wave d-epending an the ahape' of t h e bottom of t h e 'float The' magnitude of the D p c t . depende . m a i n l y on t h i s mve, and on the magnitude of the wetted surface which lies bohind it: In the present paper @ . m e t h o d ie described fa?. . the meamrainent,of ths wetted eurface'of the P l a t . Aithon

The methods used at the M a r i n e Aircraft Experimen$al'Ec&ablishme+ f o the ~ deteminatim of gross.w e , i g h t position of the center of gravity,. of the h y b w c and aerodyslgtmic perfom+ ance"of ,fULl-size s e a p ~ e s and f.$y,fngb a % eare. described. : .' a n d

.245REHXRCH Technique

Sane preliminary' experiments have been made in which models of a propoeed jet-propelled seaplane fighter were catapulted in f r e e flight on to still water. Motion-picture recorda of the landings were made and t h e reeults anauzed to give the trim llmits of stab i l l t y and curves of t r i m plotted against speed. The spray and general handling characteristics were observed visually. The stability characteristics of the models were simLlar to those of other models and of W i z e flying boats.